Stripping a person’s natural hair color and then applying a new color is called double process hair dyeing. It is generally done when changing from a dark hair color, like brunette, to a much lighter, blond color. This two-step color change process is permanent, and the natural color will be noticeable as the roots of the hair grow out again.
In a double process hair color change, the first step is known as bleaching. Ammonia and peroxide are used to strip most of the natural color out of the hair. It is important to keep the bleach solution away from the scalp to avoid skin irritation. At this point, the hair will most likely look yellow or orange.
Toning occurs when the new color is added during the second step. The new hair color mixes with the small amount of natural color molecules left in the hair. The resulting combination is the new permanent color that cannot be washed out.
Since the new color reacts with a person’s natural hair, the same hair dye can look different on each person. A strand test is recommended to preview the color. In this test, only a small piece of hair is dyed so that a person can see what the new hair color will look like before dyeing the whole head of hair.
Care must be taken to preserve and protect hair that has been dyed using a double process. Special shampoos and conditioners are available that can be keep hair color bright and protect the hair from breakage. Since the color change is dramatic, double processed hair will need frequent touch ups when hair grows out to reveal the natural color at the roots. The same process can be used to color the roots to ensure that they match the rest of the hair.
Such dramatic color changes can cause severe damage to hair. A more subtle process called single process dyeing may limit breakage. In single process, a new color is added to the natural hair color in one step. The natural color is not removed, and instead, the two colors combine to create a new hair color.
Adding color highlights is another option. Ammonia and peroxide are used on certain sections of hair to lighten it, causing a change that is often less dramatic. Highlights create a mix of natural and dyed hair colors, and they are often used around the face to make the skin tone and eye color look brighter.